Study finds even with fetal lung maturity, babies delivered prior to 39 weeks are at risk

February 10, 2011

SAN FRANCISCO (February 11, 2011) — In a study to be presented today at the Society for Maternal-Fetal Medicine’s (SMFM) annual meeting, The Pregnancy Meeting , in San Francisco, researchers will present findings that show that despite fetal pulmonary maturity, babies delivered at between 36 to 38 weeks, still have a significantly increased risk of neonatal morbidities.

The American College of Obstetricians and Gynecologists recommends that fetal pulmonary maturity be documented for scheduled deliveries occurring prior to 39 weeks of gestation in order to prevent neonatal respiratory problems.

“We wanted to do the study because recent evidence suggests that deliveries prior to 39 weeks may result in increased neonatal morbidity,” said Yu Ming Victor Fang, M.D., one of the study’s authors. “We wanted to examine whether neonates who were delivered at between 36 to 38 completed weeks with confirmed fetal pulmonary maturity would be at increased risk for neonatal morbidities when compared to those that were delivered at 39 weeks or greater.”

To compare neonatal outcomes, the team looked at mothers who had positive fetal lung maturity tests at between 36 to 38 completed weeks. They compared the neonatal outcomes from these scheduled deliveries prior to 39 weeks with known fetal lung maturity to the outcomes from scheduled deliveries at 39 weeks to 41 completed weeks.

The study was a retrospective cohort study from a single institution over a 12 year period. Neonatal outcomes of women who were delivered following documented fetal pulmonary maturity at 36, 37, and 38 weeks were compared to women undergoing a scheduled delivery at 39, 40, and 41 weeks. A lamellar body count of ≥36,000, lecitin/sphingomyelin (L/S) ratio >2.0, or a phosphotidyglycerol (PG) of 0.3 were considered mature. Neonatal outcomes examined included: neonatal intensive care unit (NICU) admission, length of stay (LOS) in the NICU, total neonatal respiratory morbidity (Tot resp morbid), cases of respiratory distress syndrome (RDS), transient tachypnea of the newborn (TTN), other respiratory morbidity (other resp morbid), neonates requiring mechanical ventilation (Vent), proven sepsis (Sepsis), hypoglycemia, and neonatal deaths. Fetuses with major congenital anomalies were excluded. Neonatal outcomes between the two groups were compared using the chi square test.

“Patients need to be counseled carefully if they choose to have a scheduled delivery prior to 39 weeks,” said Dr. Fang. “Even if tests indicate that their baby’s lungs are mature, delivery prior to 39 weeks is not without risks.”

For interviews or a copy of the abstract please contact Vicki Bendure at [email protected], or 202-374-9259.

The Society for Maternal-Fetal Medicine (est. 1977) is a non-profit membership group for obstetricians/gynecologists who have additional formal education and training in maternal-fetal medicine. The society is devoted to reducing high-risk pregnancy complications by providing continuing education to its 2,000 members on the latest pregnancy assessment and treatment methods. It also serves as an advocate for improving public policy, and expanding research funding and opportunities for maternal-fetal medicine. The group hosts an annual scientific meeting in which new ideas and research in the area of maternal-fetal medicine are unveiled and discussed. For more information, visit www.smfm.org.